In recent years, a high speed printing with high resolution has been demanded for an inkjet type printer. As a method for forming components of an inkjet type recording head used for the above printer, some printers employ a semiconductor process used for a silicon substrate and the like, which is a fine processing technology in a micromachine field. As one of such components of an inkjet type recording head, there has been known a nozzle plate, in which a nozzle orifice (a through hole having one opening as an ejection port), which ejects liquid droplets, is formed by etching a silicon substrate.
As a method for carrying out an etching processing having high selectivity in a vertical direction (in a thickness direction) of a silicon substrate, it has been known an anisotropic etching process in which etching and side wall protection film formation (deposition) are alternately repeated. (For example, refer to Patent Document 1.)
As a deep groove formation technology of silicon by such the anisotropic etching process, it has been known a technology called the “Bosch process”. For example, in Patent Document 2, as a method for forming a nozzle orifice on a silicon substrate, a nozzle orifice is formed by the Bosch process using the ICP (Inductively Coupled Plasma) type RIE (Reactive Ion Etching) apparatus.
The Bosch process forms an orifice by carrying out etching with repeating an etching step and deposition step as described above. It has been known that the side wall of the orifice thus formed creates a wavy pattern, called “scallops”, which is recognized on a surface of a scallop (refer to Patent Document 3). By satisfying a formula b/a≧1.7, wherein the depth of the concave portion and the cycle between the convex portions of the above wavy pattern are set to be “a” and “b” respectively, the wavy pattern formed on the side wall is allowed to be muffled (smooth).    Patent Document 1: Japanese Patent application Publication (hereinafter referred to as JP-A) No. H2-105413    Patent Document 2: JP-A No. 2005-144571 (pp. 5-6)    Patent Document 3: JP-A No. 2006-130868